package org.apache.lucene.index;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.File;
import java.io.FilenameFilter;
import java.util.HashSet;

/**
 * Filename filter that accept filenames and extensions only created by Lucene.
 * 
 * @author Daniel Naber / Bernhard Messer
 * @version $rcs = ' $Id: Exp $ ' ;
 */
public class IndexFileNameFilter implements FilenameFilter {

	static IndexFileNameFilter singleton = new IndexFileNameFilter();
	private HashSet extensions;
	private HashSet extensionsInCFS;

	public IndexFileNameFilter() {
		extensions = new HashSet();
		for (int i = 0; i < IndexFileNames.INDEX_EXTENSIONS.length; i++) {
			extensions.add(IndexFileNames.INDEX_EXTENSIONS[i]);
		}
		extensionsInCFS = new HashSet();
		for (int i = 0; i < IndexFileNames.INDEX_EXTENSIONS_IN_COMPOUND_FILE.length; i++) {
			extensionsInCFS
					.add(IndexFileNames.INDEX_EXTENSIONS_IN_COMPOUND_FILE[i]);
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see java.io.FilenameFilter#accept(java.io.File, java.lang.String)
	 */
	public boolean accept(File dir, String name) {
		int i = name.lastIndexOf('.');
		if (i != -1) {
			String extension = name.substring(1 + i);
			if (extensions.contains(extension)) {
				return true;
			} else if (extension.startsWith("f") && extension.matches("f\\d+")) {
				return true;
			} else if (extension.startsWith("s") && extension.matches("s\\d+")) {
				return true;
			}
		} else {
			if (name.equals(IndexFileNames.DELETABLE))
				return true;
			else if (name.startsWith(IndexFileNames.SEGMENTS))
				return true;
		}
		return false;
	}

	/**
	 * Returns true if this is a file that would be contained in a CFS file.
	 * This function should only be called on files that pass the above "accept"
	 * (ie, are already known to be a Lucene index file).
	 */
	public boolean isCFSFile(String name) {
		int i = name.lastIndexOf('.');
		if (i != -1) {
			String extension = name.substring(1 + i);
			if (extensionsInCFS.contains(extension)) {
				return true;
			}
			if (extension.startsWith("f") && extension.matches("f\\d+")) {
				return true;
			}
		}
		return false;
	}

	public static IndexFileNameFilter getFilter() {
		return singleton;
	}
}
